The present invention relates to a semiconductor device and a method of manufacturing the same and can be used appropriately for a semiconductor device having, e.g., a memory element and a method of manufacturing the same.
As an electrically writable/erasable nonvolatile semiconductor storage device, an EEPROM (Electrically Erasable and Programmable Read Only Memory) has been widely used. Such a storage device represented by a flash memory currently used widely has, under the gate electrode of a MISFET, a conductive floating gate electrode or a trapping insulating film surrounded by an oxide film. A charge stored state in the floating gate or trapping insulating film is used as stored information, which is read out as the threshold of the transistor. The trapping insulating film indicates an insulating film capable of storing therein charges. Examples of the trapping insulating film that can be mentioned include a silicon nitride film. By the injection/release of charges into/from such a charge storage region, the threshold of the MISFET (Metal Insulator Semiconductor Field Effect Transistor) is shifted to cause the MISFET to operate as a storage element. When a trapping insulating film such as a silicon nitride film is used as a charge storage region, advantages are offered such that, due to discrete storage of charges therein, the data retention reliability thereof is higher than in the case of using a conductive floating gate film as the charge storage region, that the higher data retention reliability allows reductions in the thicknesses of oxide films over and under the silicon nitride film, and that a voltage for a write/erase operation can be reduced.
Each of Japanese Unexamined Patent Publications Nos. 2008-78387 (Patent Document 1) and 2003-68897 (Patent Document 2) describes a technique concerning a semiconductor device having a nonvolatile memory.